Industrial controllers are special-purpose computers utilized for controlling industrial processes, manufacturing equipment, and other factory automation, such as data collection or networked systems. In accordance with a control program, the industrial controller, having an associated processor (or processors), measures one or more process variables or inputs reflecting the status of a controlled system, and changes outputs effecting control of such system. The inputs and outputs may be binary, (e.g., on or off), as well as analog inputs and outputs assuming a continuous range of values. Control programs may be executed in a series of execution cycles with batch processing capabilities.
Measured inputs received from such systems and the outputs transmitted by the systems generally pass through one or more input/output (I/O) modules. These I/O modules serve as an electrical interface to the controller and may be located proximate or remote from the controller including remote network interfaces to associated systems. Inputs and outputs may be recorded in an I/O table in processor memory, wherein input values may be asynchronously read from one or more input modules and output values written to the I/O table for subsequent communication to the control system by specialized communications circuitry (e.g., back plane interface, communications module). Output modules may interface directly with one or more control elements, by receiving an output from the I/O table to control a device such as a motor, valve, solenoid, amplifier, and the like.
Various control modules of the industrial controller may be spatially distributed along a common communication link in several racks. Certain I/O modules may thus be located in close proximity to a portion of the control equipment, and away from the remainder of the controller. Data is communicated with these remote modules over a common communication link, or network, wherein modules on the network communicate via a standard communications protocol. Many industrial controllers can communicate via network technologies such as Ethernet (e.g., IEEE802.3, TCP/IP, UDP, EtherNet/IP, and so forth), ControlNet®, DeviceNet® or other network protocols (Foundation Fieldbus (H1 and Fast Ethernet) Modbus/TCP, Profibus) and also communicate to higher level computing systems. Industrial controllers utilize the aforementioned technologies along with other technology to control multiple applications ranging from complex and highly distributed to more traditional and repetitious applications.
At the core of the industrial control system, is a logic processor such as a Programmable Logic Controller (PLC) or PC-based controller. Programmable Logic Controllers are programmed by systems designers to operate manufacturing processes via user-designed logic programs or user programs. The user programs are stored in memory and generally executed by the PLC in a sequential manner although instruction jumping, looping and interrupt routines, for example, are also common. Associated with the user program are a plurality of memory elements or variables that provide dynamics to PLC operations and programs. These variables can be user-defined and can be defined as bits, bytes, words, integers, floating point numbers, timers, counters and/or other data types to name but a few examples.
User Interfaces are often employed to interact with controllers when creating and downloading user programs. In addition, control processes are often monitored from the interfaces, wherein one or more of the controller variables may be adjusted by an operator during the control process. In many aspects however, these interfaces are somewhat inflexible to the controller environments supported and the features offered therein.
Currently, there are many proprietary communications formats for exchanging data with industrial control systems and associated embedded devices. These devices typically require custom software that is substantially inflexible in nature and is not easily supported by remote locations and/or devices. One attempt at providing communications to remote stations and users from a control environment has been via e-mail notification. As such, if an electronic notice is sent out from a controller station to a plurality of remote locations, the notice is generally delivered in a unidirectional manner whereby users may be notified in isolation from other users, and communications are generally limited to notifying users that a problem has occurred without affording the opportunity to gain further information from the controller, let alone other interested parties. If an e-mail were attempted in the form of a reply to the notice, the non-real time nature of the reply may lead to serious consequences if further problems develop in the control environment (e.g., delivery of an e-mail has an undetermined time of receipt from sender to receiver). Moreover, e-mail systems are generally hard-coded at the control end, wherein changes to such systems can involve considerable expense and design.